Lake Minnewaska -- a popular, 7,000-acre lake near Glenwood, Minn. -- has been declared infested with zebra mussels after a second mussel was found there last week.

And another invasive species -- faucet snails -- has prompted Minnesota and White Earth tribal conservation officials to urge anglers, boaters and bait-gatherers to be increasingly watchful following the detection of the invasive mollusk in ponds in Otter Tail and Becker counties.

The Lake Minnewaska zebra mussel finding, confirmed Friday, spells further trouble in Minnesota's efforts to control the spread of the invasive species, because the lake is the first in the Minnesota River watershed to be infected.

"The lake flows into Lake Emily and then the Chippewa River, which flows into the Minnesota River near Montevideo," said Nathan Olson, Department of Natural Resources invasive species specialist in Fergus Falls.

Zebra mussels produce microscopic larvae called veligers, which could float downstream contaminating the Minnesota River as it flows across southwestern Minnesota to the Twin Cities.

Perhaps infested for three years

Lakeshore residents recently found an adult zebra mussel attached to a boat seat mount that was submerged in the water. On Thursday, DNR officials using snorkels found a second zebra mussel 3 miles away attached to a rock. They searched again Friday, but found no more.

Though those are the only two zebra mussels found, Olson said their distance and age indicate the lake has been infested for at least three years. And the lack of zebra mussels doesn't mean there's not many more in the lake.

"This is typical of a new infestation," Olson said. He said there's no reason the invasive species won't thrive in the lake and become much more abundant.

Olson said the DNR will do thorough checks later this summer and fall, especially looking at boat lifts and docks pulled from the water that might have zebra mussels attached.

It was the second major lake in the past 10 days to be infected. Last week, officials found zebra mussels in Pelican Lake near Brainerd in Crow Wing County. The tally now is 28 lakes and nine rivers infested with zebra mussels.

The Lake Minnetonka Association, criticizing the DNR's efforts to control invasive species as inadequate, recommended Friday a plan calling for around-the-clock invasive species surveillance at the lake's boat landings, reduced access, boat user fees, increased fines for violations and more public funding to control and prevent invasive species. Zebra mussels were detected in Lake Minnetonka in 2010.

Faucet snails imperil ducks

The faucet snails found in Otter Tail and Becker counties have been known to carry a parasite that killed thousands of ducks on Lake Winnibigoshish in 2007 and 2008. The DNR is in the process of making it illegal to possess the snails, which in this instance were first found in containers with water with leeches that had been collected locally and were being sold for bait.

The ponds the snails were found in are used for duck hunting and leech-collecting.

DNR officials are asking anglers and bait-collectors to thoroughly inspect equipment and bait containers for faucet snails, as well as any other aquatic invasive species, to further prevent their spread.